Recently, according to rapid increase in demands for portable electronic products, such as laptop computers, video cameras, portable phones, etc. and earnest development of electric cars, storage batteries for energy storage, robots, satellites, etc., studies of high performance secondary batteries capable of repetitive charging and discharging are actively conducted.
Currently commercialized secondary batteries are nickel cadmium batteries, nickel hydrogen batteries, nickel zinc batteries, lithium secondary batteries, etc. and the lithium secondary batteries thereamong are receiving attention according advantages of free charging/discharging, a very low self-discharge rate, and high energy density since a memory effect is barely generated compared to nickel-based secondary batteries.
Meanwhile, a power system is essential in various apparatuses that require electric energy, such as electric cars. The power system is in charge of stable power supply between a battery and a load by selectively closing or opening at least one contactor.
In relation to safety of the power system, it is required to diagnose generation of largely two types of accidents. One is a current leakage accident of a battery and the other one is a short circuit accident of a contactor. When the current leakage accident is generated, a user has a risk of getting an electric shock or the like, and when the short circuit accident is generated, there is a risk of sudden unintended acceleration or the like.
A conventional art for diagnosing the current leakage accident and a conventional art for diagnosing a short circuit accident have been easy disclosed, but a conventional art for simultaneously diagnosing two types of accidents is not disclosed.
A critical safety problem may be generated if the current leakage accident and the short circuit accident are not simultaneously diagnosed. For example, when a diagnosis of the short circuit accident begins after a diagnosis of the current leakage accident is completed, generation of the short circuit accident cannot be quickly notified to a user.